The art of synthesizing DNA has progressed to include automated instruments for concurrently producing multiple DNA segments, that is, oligodeoxyribonucleotides, a term that is frequently shortened to oligodeoxynucleotides and shortened further to oligonucleotides. These machines often make use of reaction columns in which a support material for the reaction is positioned within the columns between inert, porous filters, referred to as "frits." The reaction columns are placed within the automated apparatus so that chemicals can be added to the columns in sequence and in appropriate amounts in an automated fashion. The object is to synthesize the desired oligonucleotides from a starter material bound to the support.
Currently known automated synthesizers can produce only a few oligonucleotides at a time limited by the number of reaction columns located within the machines. The number of reaction columns is limited as a practical matter by the increased complexity of the plumbing and valving network as the number of columns increase since currently known synthesizers provide a tightly plumbed network from the several reagent supply reservoirs to each reaction column. As a result, conventional automated synthesizers typically provide for automated synthesis of only one to four primer length (typically 20-mer) oligonucleotides in several hours. If a four column unit is operated three times in an 8-hour workday, twelve primers can be produced. To produce 100 oligonucleotide primers per day requires eight of these expensive machines. Also, the cost of the expensive reagents and the labor associated with the synthesis of 100 primers is high. While improvements in the production of primers holds great promise for research and development activities in many areas, including, for example, the effort needed to sequence the entire human genome, the automated synthesizers currently available are inappropriate for many applications in terms of throughput, operating costs and yields.
In addition to the production of primer length oligonucleotides currently known synthesizers can produce much longer oligonucleotides, i.e., greater than 100 nucleotides in length. The time to produce a 100 nucleotide DNA is approximately five times longer than the production of a 20 nucleotide DNA.
It is, therefore, an object of this invention to provide an instrument that uses considerably less reagent material for equivalent yields, reduces labor cost in the operation, keeps the initial expense of the machine within reasonable limits by limiting the complexity of the machine and enables the production of hundreds of primers each day.